The present invention relates to a simplified ballast control circuit for use with a fluorescent lamp. In particular, the present application relates to a fully functional ballast control circuit with a simplified design that eliminates complexity and cost.
Conventional ballast control circuits include a wide variety of features, however, these circuits tend to be rather complex. For example, conventional ballast control circuits usually set a preheat time and frequency to allow for preheating of the lamp filaments, a frequency sweep from the preheat frequency to the resonance frequency of the resonance output stage such that the lamp ignites and a final run frequency at which the lamp is provided with the correct power for normal operation. These various frequencies are typically generated by the ballast control circuit using a voltage controlled oscillator (VCO) which provides different frequencies for an output operating signal based on a voltage level provided at the input of the VCO. Another timing circuit is usually provided to program the time period during which the operating signal remains at each of the frequencies described above, and yet another circuit is typically provided to program the sweep time between each frequency. Thus, conventional ballast control circuits must include a substantial amount of additional circuitry just to allow for changing of frequencies in the circuit. As a result, conventional ballast control circuits tend to be somewhat complicated, and thus, it is sometimes difficult to determine exactly how they function, which can complicate maintenance and/or trouble shooting. In addition, the complexity of the conventional ballast circuits adds substantial cost to their manufacture.
Accordingly, it would be beneficial to provide an improved ballast control circuit that avoids the problems mentioned above.